The fracture shown is a triplane fracture which is an external rotation injury that occurs in patients during early adolescence as described by Spiegel et al in a retrospective review of 237 cases. Kay et al has a nice review of pediatric ankle fractures. CT scans are usually obtained for these fractures and treatment depends on the amount of displacement.
Kay RM, Matthys GA. Pediatric ankle fractures: evaluation and treatment. J Am Acad Orthop Surg. 2001 Jul-Aug;9(4):268-78.
PMID:11476537 (Link to Abstract)
Spiegel PG, Cooperman DR, Laros GS. Epiphyseal fractures of the distal ends ofthe tibia and fibula. A retrospective study of two hundred and thirty-seven casesin children. J Bone Joint Surg Am. 1978 Dec;60(8):1046-50.
PMID:721852 (Link to Abstract)